Quick break electric switches



July 3, 1956 J. w. ANDERSON 2,753,413

QUICK BREAK ELECTRIC SWITCHES Filed Sept. 28, 1955 Ful?. 4 50 72 114 4240 30 54 41126 23 2 2 4;; 114 .152 ,2 W 110 41130 u n n K IIA l Mgg 3030/////'j 413/ 1 g g ff "I1 f1. ff A 1&3 4p 64 gz 103 14 1f :44 102 112100203i 50 15 52 go 74 114 42 40 3'( a@ 25 ,55/ 77 52 i4 72 l l lli 53 M034 12 15a //l Z6 ya y/ 9121; I, A :X32 Z 60M l L ,d A`- TT 133 105 l A WY .96

f 3s IZ INVENTOR.

Jahn W Hndfl'sn United States Pate-nt O QUICK BREAK ELECTRIC SWITCHESlohn W. Anderson, Westfield, N. I., assignor to Airtron, Inc., Linden,N. J., a corporation of New Jersey Application September 28, 1953,Serial No. 382,635 19 Claims. (Cl. 200--73) This invention relates toelectric switches wherein provision is made for the instantaneous,complete or substantial separation of contact members to minimize orobviate objectionable arcing.

An important object of this invention is the provision, in such aswitch, of improved means by which one contact of a pair of contactstherein may be wedged into and held in rrn engagement with the otherContact of the pair while, nevertheless, being capable of instantaneousseparation from said other Contact by a reverse operation.

Another important object is the provision, in such a switch, of a wedgewhich closes switch contacts as a result of operation in one directionbut automatically becomes covered and nullied insofar as wedge action isconcerned, by a sheer-drop, contact holding platform which permitsinstantaneous, substantial separation of the contacts upon reverseoperation of the wedge.

Another important object is the provision, in such a switch in which atleast one of such contacts is resiliently supported, of means forpreventing accidental inter-engagement of the switch contacts.

Another important object is the provision of an improved multiple switchstructure wherein plural switch assemblies have common operating means.

The foregoing and other more or less obvious objects are accomplished bythe present invention, of which, for illustrative purposes and withoutlimiting the invention thereto, a preferred embodiment is illustrated inthe accompanying drawing in which:

Figure l is a longitudinal partly sectional view of one form of switchstructure in which the principles of this invention are advantageouslyemployed; the section being substantially on the angularly extendingline 1-1 of Fig. 2.

Fig. 2 is an end elevational View of said switch structure, lookingtoward the right end of Fig. l. I

Figs. 3, 4 and 5 are fragmentary, enlarged views of a portion of theswitch structure of Fig. 2 showing, sequentially, the coaction ofcertain parts of the device to close the switch.

Figs. 6, 7 and 8 are views of the same character as Figs. 3, 4 and 5,showing, however, the sequential coaction of the same parts to open theswitch.

The switch structure illustrated in Figs. l and 2 preferably comprises agenerally cupashaped central terminal 12 of conductive metal having aflat circular bottom or end wall 14 and stepped cylindrical side wallportions 16, 18 and 2t) with intervening shoulders 22 and 24. A single,cylindrical, inner Contact element 26, preferably of relatively thin,flexible, conductive metal, having a circumferentially continuous baseor mounting `portion 28 and a circumferential series of integral,flexible contact fingers 30, is suitably, conductively mounted upon theterminal 12 as by having its mounting portion 2S soldered within and tothe terminals wall 20, preferably in abutment with the shoulder 24, or,as shown in the drawing, said mounting portion may be secured within thewall 20 by an internal clamping or presusre ring 32. If desired,

'ice

of course, both soldering and the clamping ring may be employed toassure a rm mounting of the contact element 26 and' good conductivitybetween the latter and the terminal 12. Each of the contact ngers 30 hasthe elongated body portion 31 extending substantially parallel to thecommon axis of symmetry of the switch and is reversely bent at its freeend to form a radially inwardly extending cam follower 34 preferablyhaving the semicylindrical bottom or radially innermost surface 33 andthe rear side surface 35, the latter extending from surface 33 to theelongate body portion 31 and substantially perpendicularly to thelatter; and the finger also has a radially outwardly facing contactpoint 36 welded, soldered, or otherwise suitably fixed to its free end.A connection post in the form of a metal stud 38 is threaded into theend wall 14 of the terminal.

ln use, the plural contact fingers 30 are connected through terminal 12.and connection post 33 to a common wire or lead (not shown) of pluralelectric circuits. Each of the fingers 3i), thus, is an inner member ofa pair of switch fingers which is radially aligned with and coacts, forswitching purposes, with one of a plurality of separate, similarradially outer, longitudinally extending, flexible contact fingers 40,each of which is in the form of a strip of suitable, flexible,conductive metal provided with a suitably mounted, radially inwardlyfacing contact point 42 in opposition to a contact point 36 of a matinginner Contact finger.

The contact lingers 40 are similarly mounted, separately, within acircumferential series of longitudinally extending, external grooves orslots 44 formed in an annular contact holder 46 formed, preferably, of asingle piece of rigid, dielectric material. The lingers 40 are secured,toward their outer ends, to a relatively thick outer end portion 43 ofthe contact holder 46 by means of inner screws 50 and outer screws 52,the latter of which are accessible exteriorly of the device to serve asbinding posts by means of which separate wires (not shown) are connectedto the contact fingers 40.

The inner end of the contact holder 46 is in the nature of an integral,sleeve-like extension 54 within which accurately fits the cylindricalwall 20 of the terminal 12 with the latters shoulder 24 abutting ashoulder or inner end 56 of the portion 48 of the contact holder 46.

Within the terminal cup 12 is disposed an annular bearing element 58,preferably of rigid, dielectric material, having a nose 60 at its outerend seating accurately within cylindrical wall 16 of the terminal 12 andabutting the inside of said terminals end wall 14, an enlargedintermediate portion 62 seating accurately within cylindrical wall 18 ofsaid terminal and abutting the latters shoulder 22, and an innercylindrical extension or bearing sleeve 64. The contact holder 46,terminal cup 12 and bearing element 58 are all held firmly togetheragainst any relative movement as, for example, by one or moretightfitting pins 66 extending radially within aligned radial bores inthe three mentioned parts. These pins, if of conductive material, shouldbe clear of contact with any of the contact fingers 40. To partiallyaugment the etfect of the pins 66, one or more pin-like metal tubes 68may extend radially with a tight t within aligned radial bores incylindrical wall 16 of the terminal cup, the nose 6) of bearing element58 and the inner end of stud 38, the bore in the latter communicatingwith an axial bore 79 in said inner stud and in the intermediate portion62 of the bearing element. Thus, the tube or tubes 68 may serve toprevent relative movement of the said terminal cup, bearing element andconnection stud and, if said tubes, as shown in the drawing, arearranged to terminate outwardly of the bore 70, a vent is provided fromthe area within the bearing sleeve 64, through bore 70 and tube or tubes68 to ambient atmosphere.

With the parts arranged and xed together as aforesaid, the contactholder 46 and the terminal cup l2 form a rear end wall of the device.Substantially coaxial with said rear end wall is a circular, front endwall 72 of suitable metal, the two said end walls being spaced by acylindrical wall or cover 74, preferably of rigid dielectric material,these parts being held together by tie rods or long bolts 76. The endsof the cylindrical wall 74 seat and are held tightly within annularrabbets 78 and 3ft formed, respectively, in the contact holder 46 andthe front end wall 72. An ring 82 of rubber, or other suitablerubber-like material, is radially compressed by the cover 74 within anouter annular groove 84 provided for said ring in the contact holder 46to prevent ingress of dirt or other foreign matter through the grooves44 to the interior of the device. lt should be observed that the seriesof inner contact lingers 3@ and the series of outer contact lingers 40,when in normal or non-flexed or open condition, are in two concentriccircles and spaced from each other. The principal features of thisinvention reside in operating means by which the fingers of one seriesor set are simultaneously liexed radially into contact with the fingersof the other series or set and by which they may be instantaneouslydisengaged, with a snap action, to obviate or minimize arcing.

The switch operating means, as illustrated in the accompanying drawing,include a manually reciprocable operating plunger 86 which has a handleSS lixed upon its outer end and extends with a close sliding fit throughan axially enlarged bearing portion 9i) of front Wall 72 and into thebearing sleeve 64. An annular actuator 92, preferably of rigiddielectric material, is lixed by pin 94 to the plunger 86, the plungerand actuator being normally urged rightwardly or rearwardly by a coilspring 96 which extends about the plunger and is compressed between thefront wall 72 and the actuator 92 to hold the latter normally inabutment with the outer end 98 of bearing sleeve 64.

The actuator 92 is so designed that when it with the plunger 86 ismanually pulled forwardly (leftwardly as viewed in the drawing),portions of the actuator function as a cam or wedge to flex the freeends of all the inner Contact lingers 30 radially outwardly intoswitching or closing engagement with the free ends of the outer contactlingers 40, the engagement of these fingers of course being throughtheir respective contact points 36, 42. This liexing is of suchmagnitude that the outer contact lingers 40 are forced to liex radiallyoutwardly to some extent so that the reaction set up therein causes themto maintain a lirm or positive switching engagement with the innercontact lingers while the latter are not bent beyond their flexinglimits by the camming or wedging action applied thereto.

To permit functioning as generally recited in the preceding paragraph,and to yield a further or additional function hereinafter described, theactuator 92 is formed with an outwardly directed cylindrical surface 100which extends from a hat, back end surface 02 of said actuator to theouter circumferential limits of a frusto-conical wedging surface 204which tapers inwardly to adjoin another cylindrical surface 196. Thelatter surface constitutes an inner side wall of an axially directedannular recess NS the outer walls or surfaces of which are a flat,annular, bottom surface 110 and another cylindrical surface 112 whichconstitutes the outer side wall or surface of the recess 10S. Thesurface 112 is part of a cylindrical, rearwardly extending tongue 114,of the actuator, which, when the latter is in its normal or switch-openposition, extends between contact points 36 and 42 to prevent accidentalclosing of the switch from vibration or other causes.

The actuator 92 is shown in Fig. l in its normal or full, switch-openposition, abutting the outer end 98 of bearing sleeve 64. The contactlingers 30 and 40, likewise, are in their normal or open positions, theshowing thereof in Fig. l being illustrative of the condition of theentire circumferential series of lingers 3l) and 40; and therelationships of all such fingers to the actuator 92 are similar becausethe detailed parts of the actuator are circumferentially continuous andannular or circular. When the switch is fully open, the tongue M4extends between and clear of the Contact points 36, i2 and the free orcontact ends of contact lingers Sil extend into the annular recess 168with the cam follower 34 extending radially inwardly into axialalignment with the wedging surface 104.

There is associated with the actuator 92 and bearing sleeve 64 anannular element 116 preferably of sheet metal and hereinafter referredto for convenience as a sliderf1 This slider is formed with an innercylindrical back-end flange i118 which encircles and engages the outercylindrical surface of bearing sleeve 64 with a rather tight butnevertheless a sliding lit. lf desired, this lit may be an easy slidinglit but may be frictionally accentun ated by providing longitudinalslots i2@ opening at the free edge of the flange it to form springlingers l22 which, but for the presence of sleeve 64, would bendinwardly, but are held to cylindrical form aggregatively by said sleeveto react thereagainst as springs and thereby oppose sliding of theslider M6 except in response to positively applied forces. The criterionof the sliding coaction of the slider with the bearing sleeve 64 is thatthe slider preferably will not slide relatively to said sleeve except ascompelled to do so by its hereinafter described relationship to theactuator 92.

The slider 116 has a radial, annular web 121i which integrates liangeill; with an outer cylindrical flange 126. The latter liange intimatelysurrounds cylindrical surface lill) of the actuator 92 in spacedrelationship to the inner contact fingers 3l) and preferably iscircumferentialiy beveled at its free edge as at 128 to the sameangularity as the Wedging surface 104.

The slider 116 is linked to the actuator 92 for limited longitudinalmovement therewith, but some lost motion therebetween is provided by thelinkage means which, as illustrated, comprise preferably at least threesimilar circumferentally equidistant linkage assemblies each comprisingan elongate gromrnet 134) having a rear end radial llange 132. Eachgrommet extends slidably through a hole provided therefor in the slidersweb 124 with its unflanged forward end held close to or embedded in theback end surface 102 of the actuator 92 by a headed screw 134 whichextends through the grommet and is threaded into the actuator 92. Thegrommet hole in the web 124 is smaller than the grommets ange 132, sothat the lost relative motion between the actuator and the slidercorresponds to the distance between the actuator surface M2 and theopposed or facing side surface of the grommets flange 132.

The enlarged bearing portion of the front wall 72 of the device may beexternally threaded to receive a mounting nut 136 which, with a relatedlock washer 13S, may serve to secure the device upon an instrument panelfragmentarily shown at i40. The bearing portion 9i? and the withinplunger S6 extend through a hole in the panel so that the switching.parts of the device are at the back of the panel while the handle 88 isreadily accessible at the front of the panel for convenient manual operation of the device. It should be understood that the device, asillustrated in the accompanying drawing, has fourteen similar switcheswhich function simultaneously in response to manual reciprocation of theplunger.

Figs. 38 more or less diagrammatically show the working parts of thefourteen switches and should afford an understanding of the manner inwhich the switches function. In considering these ligures it should benoted that the principal stationary parts are the bearing sleeve 64, thecupshaped central terminal 12 which supports the inner Contact lingers30, and the annular contact holder 46 which supports the outer contactfingers 40.

Fig. 3 shows the parts as when the device is dormant with the switchopen. To close the switch, the operator grasps handle 88 (Fig. 1) andpulls plunger 86 forwardly (leftwardly) against the yielding compressiveforce of spring 96. In a first part o-f this forward plunger movement,actuator 92 moves forwardly with the plunger but slider iid, due to itsfrictional engagement with sleeve 4, remains stationary until flange 132of the grommet engages the sliders web 124, whereafter the actuator theslider, with continued forward movement of the plunger, move forwardlyin unison lirst to their positions shown in Fig. 4 and finally to theirpositions shown in Fig. 5.

At the point of operation shown in Fig. 4, the cam follower 3d hasridden up the wedging surface 1M to bring contact point 35 into initialcontact with contact point d2; the tongue 114, meanwhile, having movedfrom its protective position between said contact points.

At the point of operation shown in Fig. 5, the cam follower 3d hasridden up the beveled edge 128 of the slider and has come to rest uponthe sliders outer cylindrical flange 26 to fully close the switch, theiiange 126 then being interposed between the cam follower 34 and theactuator 92. The resultant additional lift imparted to the contact point36 has served to flex the inner Contact arm 30 further and to flex outerContact arm 40 radially outwardly to set up in the latter an inwardlydirected reaction which assures a positive interconnection between thetwo contact tingers through their related contact points.

The operator may maintain the closed switch condition by holding theplunger 86 in its extreme forward position, but switch structures of thetype described herein are used mostly where the switch need be heldclosed only for a short or momentary period of time. After the switchhas been closed for the desired time period, the operator merely releasehis grip on the handle S8, thereby permitting spring 96 to force theactuator 92 rearwardly.

During the first part of such rearward movement of the actuator, theslider 116 remains stationary until its web 124 is engaged by the backend surface 1&2 of the actuator, as shown in Fig. 6, at which instantthe cam follower 3d is still resting upon the sliders tlange 126 and thefree margin of the latter substantially overhangs the wedging surfaceldd of the actuator.

Thereafter, the actuator and the slider move rearwardly in unison until,as shown in Fig. 7, the cam follower has dropped, radially inwardly, offthe free edge of the sliders ilange 26, this drop constituting aninstantaneous movement of the contact finger 30 from its fully closed orflexed position to its fully open or undexed position. There is norelatively gradual opening movement because the wedging surface 164, theonly structure which conceivably could cause any gradual openingmovement of the contact finger 3i), is at that time ineffective becauseit is underneath the sliders iiange 126.

Simultaneously with the described opening movement of inner contactlinger 30, the outer contact finger 4t) assumes its normal or uniiexedposition. Although these instantaneous opening movements of the twocontact lingers might tend to cause them to vibrate and thereby causetheir contact points to contact or approach each other, this possibilityis avoided because the continued rearward movement of the actuator 92causes its tongue it to project itself between said contact points assoon as the described opening movement of the contact fingers hasoccurred. Final rearward movement of the actuator 92 brings all theswitch parts to their normal or open positions as shown in Fig. 8, thesame as in Figs. l and 3,

The described, unimpeded, instantaneous opening of the switchs contactpoints prevents arcing upon the breaking of an electric circuittherethrough and the tongue 114 gives positive assurance againstaccidental closing of 6 the switch and against objectionable vibrationof the switch fingers at the instant of their opening movement.

It should be obvious that the present inventive concept may be embodiedin other switch and switch operating arrangements and, withoutattempting to recite all such possible arrangements, it may be notedthat switch operation, somewhat similar to that hereinbefore described,may be derived from rotary reciprocatory actuator movement. Therefore,the present invention is not limited to the structure shown in theaccompanying drawing but should be limited only to the extent indicatedin the following claims.

I claim:

1. A quick break electric switch comprising a resiliently supportedcontact element, an actuator movable relatively to said Contact elementand having a wedging surface adapted, upon such relative movement in onedirection, to wedge said element towards its closed position withrespect to a related contact element, and a slider associated with saidactuator and adapted, during such movement in said one direction, tomove between said actuator and said contact element to hold the latterin its closed position, and adapted, during opposite relative movementof the contact element and the actuator, to slide reiatively to thelatter to bring a portion of the slider to a position covering saidwedging surface while still thus holding the contact element; the saidslider and actuator, in their last mentioned relative positions, beingmovable in unison relatively to the Contact element, during a portion ofsaid opposite movement, to disengage the slider from the contact elementto permit the latter to move to open position independently of saidwedging surface.

2. A quick break electric switch comprising a resiliently supportedcontact element, a reciprocable actuator having a Wedging surfaceadapted, during movement of the actuator in one direction, to engage andwedge said element toward its closed position, a slider slidablyassociated with said actuator and having a contact-elementholdingportion adapted, during such one directional movement, to receive saidcontact element from said wedging surface and hold said contact elementin closed position and being capable of limited lost sliding motionrelatively to the actuator during a first part of opposite movement ofthe contact element and the actuator to enable the said wedging surfaceto move to a position underneath said contact-element-holding portionwhile the latter still holds the contact element in closed position andto discharge the latter therefrom independentiy of said wedging surfaceduring a later part of such opposite movement.

3. A switch according to claim 2, the said actuator having an integraldielectric tongue which constitutes a barrier between said contactelement and a related contact element when the former element is in anopen position and is in a removed position from the space between saidcontacts during a period when said actuator and slider are effective towedge said lirst-mentioned contact toward its closed position and tohold it in that position.

4. A switch according to claim 2, further including a fixed abutmentmember coacting with said actuator to limit the latters switch openingmovement, the slider being lost-motionedly linked to said actuator formovement therewith during parts of the actuators movement and having anintegral extension in sliding frictional engagement with a surface ofsaid abutment member to restrain said slider against material movementexcept as constrained through said linkage to move with the actuator.

5. A switch according to claim 4, wherein said linkage comprises aheaded stud extending through a hole, smaller than the studs head, insaid slider and fixed into said actuator.

6. A switch according to claim 2, the said contact element being a lirstcontact element and the device including a second resiliently supportedcontact element;

the said wedging surface being adapted to wedge said first contactelement approximately to initial closing engagement with said secondcontact element; the contactelement-holding portion of the slider beinga thin member adapted to receive said first contact element from saidwedging surface and, to the extent of its thickness, to continue theclosing movement of said first Contact element to the extent of movingthe second contact element against the resilience of its support wherebyto assure rm closing engagement of the two contact elements.

7. A quick break electric switch comprising a first, circular series ofresiliently supported switch contacts, a second, circular series ofswitch contacts, concentric to and spaced from said first series and itsContact members mating, for switching purposes, with the contact membersof the first series, an axially reciprocable, annular actuator havingcircularly arranged contact-actuating portions adapted, in one directionof reciprocating movement of said actuator, to coact with said firstseries of contacts to urge them toward said second series, an annularslider lost-motionedly linked to said actuator and having circularlyarranged holding portions adapted, during movement of the actuator insaid one direction, to engage and hold said first series of contacts inclosed association with said second series, said holding portions beingshiftable relatively to the actuators said contact-actuating portions tocover the latter, during a first part of opposite movement of saidactuator, and adapted, atan intermediate point in such oppositemovement, to move from holding association with the said first series ofcontacts to release them past and out of contact with saidcontact-actuating portions of the actuator.

8. A switch according to claim 7, the said lost motion linkagecomprising plural studs, fixed to said actuator at variouscircumferential points therearound and extending from an axially facingsurface of said actuator through holes in said slider and having headsspaced from said axially facing surface of the actuator and adapted withthe latter surface to limit relative movement of the actuator and theslider.

9. A switch according to claim 7, further including an annulardielectric sleeve, movable, with said actuator, between one position inwhich it extends between said two series of switch contacts and anotherposition in which it is clear of the space between said two series.

10. A switch according to claim 7, further including a reciprocableplunger to which said actuator is fixed for reciprocation therewith, andan abutment sleeve constituting a bearing for said plunger and anabutment for limiting the actuators said opposite movement and having anouter cylindrical surface; the said slider having a sleeve in slidingfrictional engagement with said cylindrical surface, restraining saidslider against material movement except as derived from said actuatorthrough the mentioned linkage.

ll. A switch according to claim l0, the sliders said sleeve havingplural spring fingers in yieldable sliding engagement with the abutmentsleeves said cylindrical surface.

12. A quick break electric switch comprising, the combination with afirst contact point, of a second contact point, a fiexible fingersupporting the latter and comprising a body portion and a cam followerextending downwardly therefrom, said cam follower having a bottomsurface and a rear surface leading from said bottom surface to said bodyportion and extending substantially perpendicularly thereto, an actuatorreciprocable between a rear and a front position, said actuator having acam surface wedgingly moving said bottom surface to close said secondcontact point as said actuator moves frontwards, a slider mounted onsaid actuator for movement therewith and for sliding motion relativethereto between a front and a rear position, said slider in its rearrelative position and upon further frontward movement of said actuator,having a portion interposed between said actuator and said flexiblefinger and means retaining said slider stationary while said actuatorbegins its rearward movement and until said actuator is at its rearlimit of motion relative to said slider, whereby said cam surface inmoving under said cam follower is separated therefrom by said interposedportion and when said actuator moves further backward, carrying saidslider with it, said bottom surface and said rear surface fallprecipitately past the rearward moving front and of said interposedportion and past said cam surface and out of contact with the latter, toquickly break the contact of said contact points.

13. A switch according to claim 12, said actuator further comprising adielectric tongue extending between said contact points in the rearmostposition of said actuator, said tongue having a fixed position relativeto said actuator and being withdrawn from between said points as saidactuator moves forward.

14. A switch according to claim 12, said slider retaining meanscomprising a stationary member and friction means comprised by saidslider and frictionally engaging said stationary member.

l5. A switch according to claim 12, said first contact point furtherhaving resilient supporting means and being displaced from its opencircuit position by said second contact point upon said further forwardmotion of said actuator and intel-position of said portion of saidslider, and against the resilient reaction of said resilient supportingmeans.

16. A quick break electric switch comprising, in combination, a firstcircular series of co-ntact points, an elongate flexible contact fingersupporting each of said points, a second circular series of contactpoints located radially inside said first series and mating therewithand an elongate flexible contact finger supporting each point in saidsecond series, said fingers of said second series having elongate bodyportions and radially inwardly extending cam follower portions, thelatter having inmost semicylindrical surfaces and rear side surfacesextending from said last mentioned surfaces to said body portions andextending substantially perpendicularly to the latter, all of saidfingers extending substantially parallel to a common axis, a stationarybearing sleeve located on said axis, a plunger mounted in said bearingsleeve for axial reciprocation, an annular actuator fixed on saidplunger, said actuator having a forward cylindrical surface, a rearward,larger cylindrical surface, and a frusto-conical cam surface joiningsaid two cylindrical surfaces, a slider mounted on said actuator andhaving a flange portion surrounding and slidably engaging said largercylindrical surface, means limiting the sliding motion of said sliderrelative to said actuator, and means tending to maintain said sliderstationary while said actuator moves relative thereto within the limitsimposed by said limiting means, said slider moving in unison with saidactuator when the latter moves past the limits of relative motionbetween said actuator and said slider, said actuator upon forward motionengaging said cam foliowers by said cam surface to wedge said secondseries of contact points into closed position against said first seriesof points, said actuator upon further forward motion interposing saidfiange of said slider between said cam followers and said largercylindrical surface, said cam surface upon rearward motion of saidactuator moving into substantial radial alignment with said flangeportion and being radially inside the latter while said cam followerrests on the outer surface of said flange, and further rearward motionof said actuator carrying said slider rearward to release said camfollowers suddenly past said flange portion and said cam surface and outof contact with the latter.

17. A switch according to clann 16, said motion limiting meanscomprising a radially extending web comprised by said slider, a rearradial surface of said actuator engaging said web to produce rearwardmotion of said slider, said web being formed with a plurality ofperforations,

and a plurality of parallel, elongate grommets fixed in said actuatorand extending rearwardly from said rear radial surface through saidperforations and having heads engaging the rear surface of said web toproduce forward motion of said slider.

18. A switch according to claim 17, said slider rurther comprising aplurality of spring fingers extending rearwardly from said radial weband frictionally engaging the outer surface of said bearing sleeve, saidfingers and bearing sleeve constituting said means tending to maintainsaid slider stationary.

19. A switch according to claim 16, said actuator further comprising anannular, rearward extending dielectric tongue, said tongue constitutingthe outside wall 0i an annular recess formed in said actuator, theinside wall o said recess being said forward cylindrical portion, saidsecond series of Contact points extending into said recess in the rearposition of said actuator and said tongue being interposed between saidtwo series of points to prevent accidental contact therebetween.

References Cited in the tile of this patent UNITED STATES PATENTS2,471,568 Harrison May 21, 1949

